Thermal recording sheets employing the color development reaction of leuco dye and a coloring agent are relatively inexpensive, and in addition, recording devices for such thermal recording sheets are compact and easy to maintain, and therefore, are widely used as recording mediums for facsimiles and recording mediums for printers for word processors and computers.
In addition, thermal recording sheets having excellent transparency and quality of recorded images have recently been used as recording mediums which substitute silver films for recording medical images, such as medical radiographs.
A notch is provided in a certain place in conventional silver films for recording medical images, in order to facilitate accurate differentiation of front and rear faces, as well as left and right, of the film when handling the film in a darkroom (see Patent Document 1).
Likewise, in the case of a thermal recording sheet, the higher the transparency thereof is, the more difficult it is to differentiate between the recording surface and the rear surface. In the case where an image is recorded on a thermal recording sheet, in general, an image recording device such as a printer is used, and the thermal recording sheet is loaded in a sheet storing portion of the image recording device. However, the loading operation of thermal recording sheets in the image recording device is troublesome, and mistakes easily occurs in the loading operation of sheets in the case that it is difficult to differentiate between the recording surface and the rear surface of the thermal recording sheets.
In addition, in the case where an image is recorded on a thermal recording sheet employing an image recording device, it is necessary to accurately set a large number of thermal recording sheets in the sheet storing portion of the image recording device, and therefore, a bundle of thermal recording sheets which are integrated with wrapping are usually loaded in the sheet storing portion as a thermal recording sheet pack.
In addition, conventional thermal recording sheet packs are intended to have such a configuration as to be usable with as small floor space as possible (see Patent Document 2).
In recent years, image recording devices where thermal recording sheet packs can be placed vertically as well as horizontally (also referred to as being placed flatly) have been developed taking saving of space into consideration. In the case that a thermal recording sheet pack is used when placed vertically, however, it is necessary to set a bundle of thermal recording sheets standing in the sheet storing portion of the image recording device, and therefore, a problem arises with conventional thermal recording sheet packs, such that it is difficult to set the pack accurately.
Patent Document 1: Japanese Utility Model Publication No. 2549363
Patent Document 2: Japanese Laid-Open Patent Publication H10-157704